replacement cone/coil kits for monitor 10, 6.5" mid/woofers?

Gardenstater

jayward wrote: »

I have no idea what that is, but I'm sure it's a good thing.

Polk currently thinks so. From audioholics R700 review:

Getting into the bass drivers, the R700 uses two 8” polypropylene cones with some beefy half-roll surrounds that look like they could move plenty of air if given the opportunity. One interesting design detail about the bass drivers and midrange driver is that they use dual opposite-facing spiders so that any one-way bias in excursion by one spider is negated by the other spider. This should lower even-order harmonic distortions as well as do more to keep the voice coil aligned and restricted from lateral movements. The midrange and bass drivers also use shorting rings in order to reduce induction effects, which again broadens their bandwidth and reduces distortion.

jayward

Nice! I'll have to buy some soon. Hoping to get to this over the winter. I admit, I'm still a bit intimidated by this project.

jayward

Thanks for the details. I sorta get it now. LOL. While I love sound, and playing around with this stuff, the specs aren't really my strong suit.

xschop

The wuhan MW coils have landed. These Spec'd out to 6.6 ohms each and fit the MW spud-jig perfectly, so no clearancing of the pole shaft its needed...

Gardenstater

^^Nice! I'm curious about the height of the coil and how it compares. Also O.D.

xschop

0.50" coil length
1.060" coil OD
1.40" total length

These would also work in and clear a factory 6500.

I really like the extra 4 holes for cooling too.

xschop

Another problem I've found in some drivers is that the QC at Polk was iffy on some when they positioned and glued the VC's as their coil to base-plate depths are all over the place.

Every driver I've measured has a 0.23-0.25" thick baseplate so a 0.5" coil length should glue and set with 0.125" coil showing on the magnet side.

Gardenstater

Mine only show around 0.050" and to make them show 0.125" you have to push on the cone which results in the spider being visibly dished concave. That was a. ssembly error.

Not to mention the coils being cocked. I have to exert significant torque to make them perpendicular which also distorts the surround visibly in the process.

I'm putting in the warranty claim right now

Gardenstater

Maybe better to post this here:

Just for the record, on my 1979 MW6500s I measure ID: slip fit to a 1.010 plug gage. OD: not round 1.057max, 1.054 min.

Gardenstater

This is sitting on one of the 2 alignment fixtures that I built. They will come in handy for voice coil replacements. I don't know how well these photos show it up but you can hopefully see that spider is noticeably dished. I'd have to do a video to show it but the front plate is very much not flat as well. I can spin the whole driver on the fixture and you can see that light shows at various changing locations between precisely machined brass standoffs and the front plate.

xschop

You'd be better off cutting the old coil out and replacing/re-setting with the newer one. Assuming your base-plate ID is @1.072 like the 6500's I've measured, you could possibly get away without clearancing the metal plate, but then you can still have more susp. sag over time and then you are back to same situation.

Gardenstater

Yep. I just ordered the last 2 coils on eBay. Not replacing the voice coils isn't an option with these drivers. The nice thing about it is, these are superfluous drivers and will a be a lot of fun to use as test beds for modifications such as sound absorption underneath spider, shorting rings, disassembly friendly motor design, etc..

PS: I really want to get ahold of the test equipment to do proper A/B measurements too. Listening tests are subjective and need to be backed up with something to at least show that it isn't a case of "destroying" your speakers lol.